1. Field of the Invention
The present invention, in general relates to accessories for woodworking tools and, more particularly, to a guide bushing for use with a router.
Routers are well known types of devices used in the woodworking arts to cut dados, various shaped edges and corners, and other specialty types of cuts.
Routers are often used in conjunction with other types of accessory equipment to align them as desired to a work piece, for example. A common device for use with a router is called a “guide bushing”.
The guide bushing secures to the router base, proximate the cutting “bit”. The guide bushing allows for better control or securing of the router.
A typical guide bushing includes a known outside diameter. Accordingly, other accessory equipment items include a channel into which the guide bushing snugly fits. The router is then moved in the channel and its motion is thus controlled.
Alternatively, the accessory equipment includes an area into which the guide bushing fits. Perhaps some aspect of the accessory equipment is moved or the work piece is moved relative to the accessory equipment. In either situation, the action of the router is well controlled.
However, there exists a problem with guide bushings and that is a tendency for the bushing to loosen. Routers operate at high RPM and the vibration tends to loosen the guide bushings.
There is no known way to secure a guide bushing on a router. Set screws pass through a cylinder typically. They include a longitudinal axis that is perpendicular with a longitudinal axis of the cylinder that they pass through so that when tightened they can bear on another object that is concentrically disposed either inside or outside the cylinder.
The use of a set screw to bear against the threaded portion is not possible for two reasons. The first is that it is undesirable to mar the threads into which the guide bushing cooperates because this would make it difficult, or impossible, to later remove the bushing when it is not needed or to install one of a different outside diameter.
The second reason is it is not possible to access a set perpendicular screw in such a tight area. There are certain types of smaller routers that are commonly known as “trim routers”, with which it is presently impossible to even nominally tighten a conventional type of a guide bushing because the available area in a recess in the router base that is disposed around the guide bushing is so small, it is difficult to grab the bushing with any type of tool that could be used to tighten it.
While these problems occur with a variety of different types of routers, those manufactured by the company “PORTER CABLE” include a center hole in the base with a recessed portion that the instant invention is particularly applicable for use with.
When a guide bushing becomes loose, considerable damage can occur. First, because the router experiences greater tolerances between itself and the guide bushing, the router can move an increased amount relative to the work piece. This can cause the router to cut the work piece (i.e., the board) in an area that is not intended, possibly ruining the work piece.
If the guide bushing loosens entirely, the router bit can strike it, damaging the bit and the bushing, possibly even imparting energy to the bushing and propelling it as a missile.
Also, the router is no longer retained by the guide bushing and can move relative to the work piece in any direction. This is almost certain to cause damage to the work piece.
In general, the use of a guide bushing with a router is to be more precise with the positioning and movement of the router relative to the work piece. A loose or absent guide bushing is disastrous to this objective.
Accordingly, there exists today a need for a router guide bushing that helps ameliorate the above-mentioned difficulties.
Clearly, such an apparatus would be a useful and desirable device.
2. Description of Prior Art
Router guide bushings are, in general, known as shown in the PRIOR ART FIGURE. While the structural arrangements of the above described devices may, at first appearance, have similarities with the present invention, they differ in material respects. These differences, which will be described in more detail hereinafter, are essential for the effective use of the invention and which admit of the advantages that are not available with the prior devices.